Rotational shift controls are utilized in vehicles such as automobiles, tractors, construction equipment and the like to shift the transmission of the vehicles to and from a neutral position and various gears. Rotational shift controls are typically either electrical or mechanical. Electrical shift controls utilize electronic controls in which a lever coupled to a magnetic switch sends an electronic impulse to a set solenoids in the transmission to select the gear. Despite being very compact, such electronic shift controls are expensive. As a result, several cost competitive or cost efficient vehicles still utilize mechanical shift controls.
Mechanical shift controls typically include an elongate, rigid control shaft which is coupled to the vehicle transmission via an arm and an interconnected linkage. The control shaft itself is coupled to a lever. Rotation of the lever rotates the control shaft which rotates the arm to cause linear translation of the linkage which moves the transmission between neutral and geared positions. To prevent inadvertent shifting of the transmission between neutral and the geared positions caused by inadvertent rotation of the control shaft, prior mechanical shift controls have included interlocking mechanisms having a locking pin oriented perpendicular to the axis of the control shaft and moveable into an aligned detent in the control shaft such that the pin prevents rotation of the control shaft. Actuation of the locking pin is effected by depressment of a clutch pedal which is operably connected to the locking pin by cable. Because actuation of the locking pin between an engaged position and a disengaged position occurs along a direction perpendicular to the axis of rotation of the control shaft, the mechanism for actuating the pin requires a large amount of valuable space. In some cost competitive or cost efficient vehicles, the clutch pedal and the control shaft are positioned so close to one another that the required space is simply not available.
To reduce the amount of space required by the interlocking mechanism, some mechanical shift controls utilize an interlocking mechanism having a plate radially extending from the control shaft and a locking pin which is actuated in a direction parallel to the axis of the control shaft. In such interlocking mechanisms, the pin projects into or across slots or apertures which are angularly aligned with each of the geared positions as well as the neutral position. To shift between different geared positions or to shift between one of the geared positions and a neutral position, the clutch pedal is depressed which moves the locking pin out of engagement with the slot or aperture to enable the control shaft and its attached plate to be rotated to another position. Release of the clutch pedal causes the pin to once again project into or across the adjacent slot or opening to lock the rotational control shaft in place. Despite occupying less space than the interlocking mechanism which utilize a perpendicular locking pin, these parallel interlocking mechanisms still occupy a relatively large amount of valuable space about the control shaft. Moreover, such parallel pin interlocking mechanisms require that the clutch pedal be depressed for shifting the transmission from a geared position to neutral. Consequently, despite this advancement in the art, there is still a continuing need for a mechanism for a mechanical rotational shift control having an interlocking mechanism which is reliable, compact and provides for easy shifting into the neutral position.